GLOBAL WARMING

Scientists around the world are trying to determine how much of a role human activities are playing in causing rising temperatures, the hole in the ozone layer, and major changes in climate patterns - and how much of these changes are just part of the natural processes that Earth has experienced over 4.5 billion years. The changes seem to be occurring more rapidly than what we believe to be natural processes, so it is believed that human activities are responsible for the drastic changes in Earth's temperature causing global warming.

A delicate balance in nature
has evolved over billions of years
creating a livable and life-producing planet

The Sun's energy travels 93 million miles
at the speed of light
(186,282 miles or 299,792 kilometers per second)

and reaches Earth in 8.4 minutes!

93 million miles in 8.4 minutes

STRATOSPHERIC OZONE
Ozone in the stratosphere shields Earth from much harmful ultraviolet (UV) radiation.

Not all of this solar energy is absorbed on Earth's surface.
1/3 of the heat/energy is reflected back out into space,
in the form of long-wavelength, infrared radiation (low energy).

2/3 of the solar energy/heat reaching Earth from the sun is trapped inside the atmosphere by gases which absorb it. This is called the "greenhouse" effect.

Earth's atmosphere

But, not all of the longwave radiation escapes out into space, because .
the greenhouse gases absorb longwave radiation -

and again radiates it back down to the surface of the Earth causing additional warming.

Whew! It's getting toasty in here

Incoming shortwave radiation can pass through the gases in Earth's atmosphere as it travels toward Earth, but longwave radiation gets absorbed or trapped by greenhouse gases. This is similar to the "heat-trapping" glass in a greenhouse, and thus is known as the greenhouse effect..

There is concern that as concentrations of greenhouse gases increase, more heat is being re-radiated back to Earth and increasing surface temperatures.

SOLAR HEAT REFLECTED
Solar energy/heat can be reflected back into space from clouds, ice, and snow; and human-related changes and activities, such as:
development, aerosols, pavement, smoke, sulfates.

SOLAR HEAT ABSORBED AND TRAPPED
Solar energy/heat is trapped and absorbed by water vapor, carbon dioxide and other gases in the atmosphere. Gases which trap and retain solar heat in our atmosphere are called "greenhouse gases."

"In order of abundance and importance as greenhouse gases are water vapor (H₂0), carbon dioxide (CO₂), ozone (O₃), nitrous oxide (N₂O), methane (CH₄), and chlorofluorocarbons (CFCs)." (GSFC/NASA). Some gases absorb and trap more heat per molecule than others.

Earth and its atmosphere absorbs and traps heat and energy from the sun
The greenhouse effect provides a blanket of warmth enveloping earth, which we need. Otherwise we would freeze!

Without a natural greenhouse effect, the temperature of Earth would be about zero degrees F (-18°C) instead of its present 57°F (14°C). (NCDC/NOAA)

And if the temperature of Earth was around zero degrees, what would happen to our water supplies? The greenhouse effect is necessary to maintain the liquid state of water in the Earth's biosphere.

So, we need the greenhouse effect, but things are getting a little too warm.